The present invention pertains to processes and apparatus for scrubbing of air or other gases for removal of both particulate and gaseous contaminants, with a very high removal efficiency, so as to allow use of the invention for example in building HVAC systems for removal and neutralization of Bio-chem agents such as anthrax which terrorists may introduce into the air; and to remove very small particulates and gases from the air in clean rooms used in semiconductor manufacturing; and for cleaning of air in hospital clean rooms; and for cleaning of air or other gases in industrial processes, for effluent pollutant emission control and/or for removal of contaminants introduced in one stage of a process which may interfere with later process steps.
Many gas scrubbing processes and apparatus are known in the prior art, including but not limited to inventions using charged electrical droplets or otherwise using electrical forces in gas cleaning, as in processes and apparatus concerning or related to gas cleaning which are disclosed in applicant's U.S. Pat. Nos. 6,551,382B1; 6,156,098; 5,941,465; 5,147,423; 4,345,916; and 4,095,962. However, prior art inventions, though useful for many gas cleaning purposes, may not be adequate to deal with Bio-chem agents such as anthrax. And, they may not suffice to remove very small particulates, as small as 0.1 micron diameter, which may seriously interfere with semiconductor manufacturing in clean rooms, where deposit of such small particulates on a semiconductor surface may render the device inoperable.
The present invention is directed primarily to both the requirements of the semiconductor clean room manufacturing operation; and to the situation in which terrorists seek to kill large numbers of people by intentional contamination of air with deadly Bio-chem agents.
If bacterial spores such as anthrax, or viruses or deadly chemical agents such as nerve gas are introduced by terrorists into air which circulates in a building HVAC system, in order to render the air safe to breathe such deadly contaminants must be removed with a very high efficiency, of the order of 99.999%, by a suitable apparatus and process which cleans the air circulating in the HVAC system.
Although the charged droplet scrubber and method of applicant's U.S. Pat. No. 6,156,098 can remove most industry-generated air contaminants sufficiently to meet current regulatory standards for air pollution control, it would require large residence times of air exposure to scrubbing droplets, and large volume flow rates of the liquid scrubbing solution used in generation of the scrubber droplets to attain the desired contaminant removal efficiencies for semiconductor clean rooms and terrorist-contaminated air. Moreover applicant's '098 patent uses a very short range force acting between very highly charged droplet electric monopoles and electric dipoles induced in uncharged particulates, a force varying inversely as the fifth power of the droplet/particulate separation distance, '098 patent at Col. 6, line 35-Col. 7, line 4. In contrast the present invention uses the much longer range coulomb force between charged droplets and oppositely charged particulates, which varies inversely only as the square of the separation distance.
Accordingly the present invention is capable of achieving the desired removal efficiencies with much smaller residence time and much smaller volume of scrubbing liquid solution, and to very efficiently remove particulates in the 0.01 to 1 micron and greater size range.
In addition, for anti-terrorist applications including HVAC applications, some embodiments of the present invention are capable of not only capturing Bio-Chem agents, but also destroying them, by use of a dilute basic bleach solution as the scrubbing liquor. This offers an advantage over technology currently used to remove Bio-Chem agents, namely HEPA and activated carbon filters, which require maintenance and which can capture but not destroy the Bio-Chem agents.
It is not the intent of this application, by stating that certain embodiments of the present invention are suited to certain purposes or to dealing with certain problems, to necessarily limit the scope of the invention to only embodiments which are useful for said purposes or problems; it is instead the intent that the scope of the invention be determined by the claims as more fully stated below.